1. Field of the Invention
This invention relates generally to firefighting monitors and in particular to a compact segmented monitor having three nonorthogonal swivel joints, and minimal convolutions in the flowpath to reduce fluid pressure loss and to reduce overall turbulence of a discharge stream exiting from the segmented monitor.
2. Description of Related Art
A firefighting monitor is a conduit that is supplied with a pressurized fluid (usually water) at the inlet end and has a fire-fighting nozzle connected at the discharge end. The firefighting monitor's primary purpose is to allow the fluid exiting the nozzle to be redirected in both elevation and azimuth angles and then remain pointed at the desired target.
Monitors may be installed in fixed locations, may be portable devices, or may be mounted on mobile equipment such as fire trucks, trailers, and the like. Monitors in the fire service are generally fitted with a nozzle on their discharge whose purpose it is to increase the velocity of the jet and form a spray of a desired type or shape. The most common purpose of the monitor is the delivery of a straight stream over considerable distances. The usefulness of the stream is a function of the turbulence in the monitor itself.
Monitors have been classified into three basic types as follows: spherical ball-in-socket designs, bending of a flexible hose, and mutually perpendicular swivel joints. Most ball-in-socket designs develop motion through a sliding motion between the ball and socket, thus tending to have high friction to overcome. A single ball-in-socket is restricted to travels substantially less than 90 degrees from straight which limits their usefulness. Ball-in-socket devices arranged in a series allow a wider range of motion. The position of the ball joints are retained by friction alone. However, reaction forces on ball joints arranged in a series cause position to be unstable when the centerline of the nozzle reaction force does not pass through the centers of rotation.
U.S. Pat. No. 557,799 issued Apr. 7, 1896 to H. H. Gorter discloses an adjustable nozzle for hose pipes comprising in series a first curved section and a second curved section having an upper end which is a hollow semiglobular enlargement to which a nozzle is connected. The nozzle has a semiglobular enlargement which fits over the enlargement end of the second curved section and is secured to it by a trunion on each side thus forming a pivoted ball-and-socket joint.
U.S. Pat. No. 4,506,738 issued Mar. 26, 1985 to John L. Evans, et al. and assigned to Chubb Fire Security Limited of Sanbury-on-Thames, England, discloses a spherical head type liquid-projecting monitor comprising a head and housing which together define a chamber from which water is led through an inlet in the rear of the head to a passage extending through the head. The head has a frusto-spherical external surface which forms a sliding seal against an O-ring to keep the chamber watertight throughout the permitted range of pivotal movement of the head relative to the housing. The cross-sectional area of the passage within the head is approximately constant throughout its length to reduce turbulence and pressure drop. However, the axle passing through the flowpath presents a disruption to the flow causing turbulence while the ball in socket arrangement is limited to relatively limited range of motion.
U.S. Pat. No. 6,305,620 issued Oct. 23, 2001 to Antonio B. Marchese discloses a firefighting monitor having a plurality of outlet arms extending from the main inlet pipe. A main rotary joint is provided for rotating the casing and the plurality of outlet arms. Each outlet arm has an outlet rotary joint. A swiveling nozzle is coupled to each outlet arm for directing water from each outlet arm separately. Each swiveling nozzle has a ball joint having a passageway therethrough and having a handle thereon for rotating the main inlet pipe and the plurality of outlet nozzles. The main rotary joint and outlet arm rotary joint have an annular rack gear engaging a worm gear. When the outlet arm is rotated, the nozzles are rotated for vertical adjustment of the spray. However, the ball joints would be difficult to move under pressure because of the sliding motion of the ball within their sockets. In addition, the rotating joints would be difficult to move because of the eccentric loading of the nozzle reaction forces on the rotating joints.
U.S. Pat. No. 5,297,443 issued Mar. 20, 1994 to John D. Wentz discloses flexible positioning by bending a flexible hose. While the number of bends and turbulence in the flow path are minimized, in all cases the support for managing the hose relies on an external structural mechanism. This mechanism must withstand the forces of nozzle reaction, and in some cases the internal pressure of the hose itself. In addition, flexible hoses are limited by compression set properties of the flexible hose material. Adverse stresses exist within the hose for all positions other than neutral, which limits their degree of flexibility, and optimal storage position.
Because of their limitations, the use of the ball in socket devices and flexible hose mechanisms accounts for only a small percentage of the actual number of monitors commercially produced each year.
Monitors with mutually perpendicular swivel joints for use in firefighting account for the vast majority of monitors. These have been constructed with single or with twin waterways of various designs. The motion is controlled by swiveling the monitor through two mutually perpendicular axes. The line of action of the discharge trajectory is generally designed to pass substantially through both axes of rotation such that the reaction forces of the discharged fluids do not create a rotational moment on the monitor's swivel joint. Controlling the motion of the swivel joints with simple worm gear or other mechanisms are known in the art.
Monitors for use on the deck of fire trucks at flows up to 2000 GPM typically use a single waterway design. The most compact of these is the Stream Master® manufactured by Akron Brass of Wooster, Ohio. In the Stream Master® the water enters from a vertical feed pipe into the monitor, and undergoes approximately 3 bends of 90 degrees each. From here it enters the exit section where it undergoes 3 additional 90 degree bends. The water undergoes a total of 540 degrees of convolutions. Because compactness in mobile equipment design is desirable, the form of the bends in this monitor have been optimized as flattened shapes with essentially a zero inside elbow bend radius. It is doubtful that the flow area in these bends is equal to the flow area of the 4″ inlet diameter. With such an ultra contorted flow path these bends produce severe turbulence which adversely effect friction loss, stream quality and range.
Other prior art monitors are known and described in the following U.S. patents:
In U.S. Pat. No. 6,109,360 issued Aug. 29, 2000 to Thomas Mandzukia and assigned to Premier Farnell Corp. of Cleveland, Ohio, a firefighting monitor is disclosed having a rotatable extension member for adjusting the elevation of an outlet attached to the extension member while maintaining the discharge direction. Both the extension member and the outlet member are independently rotatable through an arc of at least 135 degrees in one direction from the vertical. However, this monitor has mutually perpendicular swivel joints in the same general shape and amount of convolutions in the water way as the Stream Master® of Akron Brass above.
In U.S. Pat. No. 4,674,686 issued Jun. 23, 1987 to James M. Trapp and assigned to Elkhart Brass Manufacturing Co., of Elkhart, Ind., a portable fire apparatus monitor is disclosed comprising a snap-fitting latch pin which fits beneath a swivel bearing on the monitor mount and which secures the monitor in place during firefighting operation and provides for quick connection to and disconnection from the mount. The flow path of this monitor comprises a plurality of turns which create undesirable turbulence and friction losses.
Therefore, it is desirable to have a monitor that has compact size with wide range of motion and minimal convolutions within the flowpath to minimize turbulence and friction losses.